Optical communication systems frequently require provision of optical switching and/or routing functionality. Accordingly, the extensive development and implementation of optical communication systems and networks has driven the development of various optical switching approaches and architectures, including optical crossbar switches and optical routers. A crossbar switch has M inputs and N outputs (frequently M=N, although this is not required), and is able to connect each of its inputs to any, some, or all of its outputs. Providing this level of switching flexibility is nontrivial, and conventional crossbar approaches tend to have difficulty in scaling to large M and N, especially for optical signals that are modulated at a high data rate. Various conventional crossbar switch approaches can be distinguished based on switch architecture and how/if o/e or e/o (optical to electrical or electrical to optical) conversion is performed.
For example, U.S. Pat. No. 4,074,142 considers a crossbar switch having electrical inputs and outputs. Each input is e/o converted and then optically delivered to each of N output modules by a passive optical system, where o/e conversion is performed. Switching is provided by electrically selecting which of the output module inputs is output from each module.
Another example is considered in U.S. Pat. No. 4,953,155, where the switch has optical inputs and electrical outputs. Each optical input is split (e.g., with a fiber splitter) and delivered to an array of detectors arranged in N rows, such that each row has M detectors, one for each optical input. The detectors can be selectively activated to provide switching functionality.
Another crossbar switch is considered in U.S. Pat. No. 5,037,173 which has optical inputs and outputs. Switching is performed with a spatial light modulator (e.g., a deformable mirror device).
In U.S. Pat. No. 5,072,439, a switch having optical inputs and electrical outputs is considered. Each optical input is routed to a separate detector. Selective activation and deactivation of these detectors can be employed to select which optical signal drives the switch output.
U.S. Pat. No. 5,283,844 considers a switch having optical inputs and outputs where switching is performed by altering transmission paths through a network of optical waveguides with total internal reflectance turning mirrors.
U.S. Pat. No. 5,345,326 considers a switch having optical inputs and outputs where switching is performed by splitting the optical inputs, passing each split optical input through an optoelectronic modulator, and then recombining the modulated optical signals to form optical outputs.
U.S. Pat. No. 6,680,791 considers a switch having optical inputs and outputs, where the optical inputs to the switch are o/e converted and electrically distributed to switching elements. The switching elements thus share their inputs. The switching elements also have optical inputs and outputs, and the transmittance from input to output depends on the electrical signal provided to the switching element, thereby providing switching.
In general terms, conventional switch approaches which incorporate o/e conversion followed by electrical switching tend to face difficulties relating to electrical crosstalk and isolation, especially for large switches. Conventional all-optical switch approaches tend to face difficulties with the optical switching element(s), especially for large switches.
Accordingly, it would be an advance in the art to provide optical switching having an improved scalability to large numbers of inputs and outputs.